This study is designed to assess the potential for nosocomial (i.e., patient staff) transmission of the newly described Acquired Immunodeficiency Syndrome. The populations to be studied include: 1) clinical patient-care-givers, clinical laboratory staff involved in processing and testing laboratory specimens from these patients, and 3) laboratory staff in research labs who receive specimens from these patients and work with blood and blood products from these patients. The objectives of this study are threefold: 1. To collect demographic data regarding NIH personnel involved in the care of HIV-infected patients and in the handling of specimens from these patients. 2. To collect baseline serum samples from these employees (and annual follow-up samples for HIV testing). 3. To obtain baseline and subsequent immunologic and oncologic studies on employees electing these studies who have sustained needlestick injuries or mucosal splashes with material from an HIV- infected patient.